Accurate determination of the dielectric function of thin metal films (eg. <10 nm) by ex-situ measurements is difficult, because of the discontinuous nature of thereof, and rapid oxidization upon exposure to air. While in-situ ellipsometric measurements during film deposition can avoid this complication, correlation effects complicate unique determination of film thickness and dielectric function from ellipsometric data alone [1]. While utilization of reflection Spectroscopic Ellipsometry SE data in combination with reflection Intensity (I) data has been reported as an approach to overcome the problem, a need remains for a method of determining both dielectric function and film thickness in-situ.
With the present invention in mind a Search for relevant references was conducted. The following were identified:    1. An article by McGahan et al., Thin Solid Films 234 (1993) describes correlation effects which complicate determining both dielectric function and film thickness from ellipsometic data alone.    2. An Article by An et al, Rev. Sci. Instrum. 65 (1994) described utilizing reflection SE data in combination with reflection Intensity data.    3. H. Arwin and D. E. Aspnes, Thin Solid Films 113 (1984) 101 describes use of a strong feature in the substrate dielectric function, (e.g., the Si critical point structure near 3.4 eV.    4. H. V. Nguyen, Ilsin An, and R. W. Collins, Phys. Rev. Lett. 68 (1992) 994 describes the presence of plasmon-polariton band near 3.4 eV for the 35 Å Al film, in agreement with previous reported work.    5. H. V. Nguyen, Ilsin An, and R. W. Collins, Phys. Rev. B 47 (1993) 3947 describes transition from non-metallic to metallic behavior.    6. M2000XI, J. A. Woollam Co., Inc., Lincoln, Nebr. describes a Rotating Compensator Ellipsometer system as used to obtain results reported in theis Specification.    7. B. Johs, J. Hale, N. J. Ianno, C. M. Herzinger, T. Tiwald, and J. A. Woollam, Proc. SPIE 4449 (2001) 41 describes a dual spectrograph detector system, (with Si CCD and InGaAs photodiode detector arrays).    8. R. Kleim, L. Kuntzler, and A. El Ghemmaz, J. Opt. Soc. Am. A 11 (1994) 2550 describes use of aone averaged measurements were performed to minimize systematic errors in the data.    9. B. Johs and C. Herzinger, U.S. Pat. No. 6,034,777, 7 Mar. 2000 describes compensation of window birefingence was characterized and corrected for by performing a calibration (to determine the “out-of-plane” window effects) and a model fit to data acquired on the fused silica substrates before deposition (to determine the “in-plane” window effects)    10. P. I. Rovira and R. W. Collins, J. Appl. Phys. 85 (1999) 2015 describes previously reported work in which reflection intensity data was simultaneously acquired by a spectroscopic ellipsometer system utilized the DC signal component to extract the intensity information.The following references 11, 12 and 13 describe calculating modulation ellipsometer parameters N, C, and S:N=cos 2Ψ, C=sin 2Ψ cos Δ, S=sin 2Ψ sin Δto account for the substrate induced depolarization:    11. R. Joerger, K. Forcht, A, Gombert, M. Khl, and W. Graf, Appl. Opt. 36 (1997) 319.    12. Y. H. Yang and J. R. Abelson, J. Vac. Sci, Technol. A 13 (1995) 1145.    13. G. E. Jellison Jr., Thin Solid Films 234 (1993) 416 which also describes weighting ellipsometric data according to their estimated error bars.    14. J.-Th Zettler, Th. Trepk, L. Spanos, Y.-Z. Hu, and W. Richter, Thin Solid Films 234 (1993) 402 describes use of cubic splines to parameterize a dielectric function.    15. Johs, French, Kalk, McGahan and Woollam, SPIE Vol. 2253, (1994) describes simultaneous use of reflection ellipsometry and transmission intensity signals to investigate multilayer structures.    16. Liphardt et al., U.S. Pat. No. 6,456,375, Issued Sep. 24, 2002 is disclosed to show it is known to take Transmission Data in ellipsometry.    17. Johs et al., U.S. Pat. No. 6,353,477, Issued Mar. 5, 2002 is disclosed as it identifies using A.C. (or (D.C. or comninations of A.C. and D.C.) components of electromagnetic beams in normalization.The references are numbered as the relevance each is better identified throughout this Specification by reference thereto.